Wired and wireless communications

PS/2
Earlier in the quarter I read up on the PS/2 protocol. The PS/2 devices you probably interact with most are your standard keyboard and mouse. I wanted to be able to plug a keyboard directly into my device without needing a computer in the scenario, so I figured that having experience with the PS/2 protocol would be a good idea. There are serial-to-ps/2 converters out there that one can make or buy, Some good websites explaining the protocol can be found at the following links:


My PS/2 and serial ports, looking so happy side-by-side

I got PS/2 working on its own protoboard at one point a week or so before the end of the quarter. However, when I was integrating all of the pieces of the project together, for some reason it started misbehaving. The data line, instead of ranging from 0-5 volts to indicate a 0 or 1, respectively, was ranging from 2-5 volts, and my microcontroller wasn't able to pick up the bits appropriately.

  • My (slightly inelegant) C routine for reading a PS/2 byte can be viewed here

Serial
I ended up equipping my final project with a serial interface as well. I used a Max233 chip, which is very simple and doesn't require any external capacitors or anything to be hooked up around it. Used in conjunction with a UART (USART), sending and transmitting serial data is really trivial. Here's the diagram I used to hook up my serial interface:

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